In a 2-quart pitcher, muddle halved jalapenos with the back of a wooden spoon. Stir in orange juice, tequila, orange liqueur, agave nectar, and lime juice. Cover and chill at least 2 hours or up to 8 hours.
When ready to serve, add grapefruit soda to the pitcher. Rub rims of margarita glasses with the lime wedge and dip in chili-lime salt. Fill glasses with ice cubes. Remove halved jalapenos from margarita mixture; discard. Pour margarita mixture into prepared glasses. Garnish with sliced jalapenos and/or limes.